As a nondestructive inspection method for detecting damage, which arose in a structure, with no destruction, a method of using an optical fiber is conventionally known. Moreover, as a concrete example of damage detecting method using an optical fiber, technique that an optical signal is propagated with an optical fiber attached to a structure from which damage should be detected and whether damage arose in the structure is determined by observing change in intensity of the optical signal is known (for example, refer to Japanese Patent Application Publication JP2005-321223 A and Japanese Patent Application Publication JP2005-208000 A).
An object of the present invention is to provide a damage detection system and a damage detecting method which can specify respective positions of damage more exactly even when damage arises at a plurality of positions.